In vacuum systems several flange standards exist, and the same flange types are called by different names by different manufacturers and standards organizations. Therefore, it is somewhat difficult to identify common terminology to refer to common flange types.
The ISO standard quick release flange is known by the names Quick Flange (QF), Klein Flange (KF) or NW, sometimes also as DN. The KF designation has been adopted by the International Organization for Standardization (ISO), the Deutsches Institut fur Normung (DIN) and Pneurop, a lobbying group for the European compressor and vacuum pump industry. KF flanges are made with a chamfered back surface that attached with a circular clamp and an elastomeric o-ring that is mounted in a metal centering ring.
The ISO large flange standard is known as an LF, LFB, MF or sometimes just an ISO flange. FIG. 1 illustrates a representative ISO flange. The flanges 100 are usually joined by a centering ring 110 and an elastomeric o-ring 120. An extra optional spring-loaded circular clamp or spacer ring 130 is often used around the large diameter o-rings to prevent them from rolling off from the centering ring during mounting.
The ISO large flanges come in at least two varieties. The ISO-K (or ISO LF) flanges shown in FIG. 1 are typically joined with double claw clamps 140 which clamp to a groove 150 on the tubing side of the flange. FIG. 2 illustrates the ISO-F (or ISO LFB) flanges 230 which have holes for attaching the two flanges with bolts. As illustrated in FIG. 2, two tubes with ISO-K and ISO-F flanges can be joined together by clamping the ISO-K side with single claw clamps, such as example single claw clamp 240 (having a single claw 241), which are each bolted to a hole on the ISO-F side.
Returning to FIG. 1, the double claw clamp 140 has first half 160 with first claw 161 and second half 170 with second claw 171 joined by bolt 180. A washer 190 is usually used on the bolt. First half 160 typically has a projection 200 that allows the claws of the clamp to apply pressure to the flanges 100 as bolt 180 is tightened.